The present invention relates to a desiccating agent. There hitherto has been known deliquescent salt such as calcium chloride or magnesium chloride, as a desiccating agent which can absorb moisture in air. It is necessary, however, to be packed in a container, since the salt is deliquesced with absorption of moisture in air. There is a problem that the salt flows around the container, if the container is broken or fallen. And further, when once the salt is deliquesced, it must be thrown away. Because the deliquesced salt can no longer absorb moisture again, even if the salt is sun-dried.
There has been proposed a desiccating agent, that is, calcium chloride carried on continuously porous mineral such as vermiculite or perlite (Japanese Unexamined Patent Publication No. 144021/1982). In accordance with the above-mentioned Patent Publication, there is disclosed an advantage that desiccating agent can absorb much moisture in air without decreasing absorption ratio under high humidity circumstances, but it is not sufficient in a variety of commodity forms.
As a result of study as to a desiccating agent which includes the deliquescent salt as a main component in order to eliminate the above-mentioned disadvantage, the present inventors have proposed a desiccating agent comprising a mixture of
(A) a deliquescent salt and
(B) a hydrolyzed copolymer of 50 to 99.8% by mole of vinyl acetate and 50 to 0.2% by mole of an unsaturated dicarboxylic acid in which a degree of hydrolysis of the vinyl acetate component is not less than 70% by mole
as main components.
The copolymer as the component (B) has some hygroscopic property, but the property is very low in comparison with the component (A). However, the hygroscopic property is synergistically increased by mixing the component (A) and the component (B). Also, the mixture of the component (A) and the component (B) has advantages that it is very easy to deal the mixture, because, even if the mixture is impregnated with much moisture in air under a high humidity circumstances, it is not liquefied and merely becomes a gel form, and that it is not necessary to especially be packed into a container. And further, it is possible that the gel changes again into the original form by being sun-dried under normal condition of temperature and humidity or being placed in low humidity circumstances, and it is very valuable that the gel can be circularly reused.
As a result of the further study, however, the present inventors have found that the above-mentioned desiccating agent can be repeatedly recycled at most five times to some extent. Therefore, when the above desiccating agent is used practically, it is obvious that the number of recycle of the above desiccating agent must be further increased.